1. Field of the Disclosure
The present disclosure relates to an image forming apparatus.
2. Description of the Related Art
When an image forming apparatus is configured so that sensors detect statuses of units, notification is directly provided a notification to a component corresponding to an event of changing the detected value of the sensors, and upon receiving the notification the component starts or stops an object to be controlled or changes display of an operation panel, the configuration of the image forming apparatus is complex, and if a sensor is newly added, changed, or deleted for a new machine type, then a signal line of the notification must be added, changed, or deleted; and it results in increasing the cost.
Therefore, the configuration is adopted in which a status collective management unit receives various status changes at one part and transfers it to a main controller by serial transmission, and transmits a notification from the main controller to a corresponding component; and in development of a new machine type, in order to cope with adding, changing, or deleting a status as a notification object, the status collective management can be modified by changing its software.
However, if two statuses are changed at a substantially same time and notification receiving processes are performed in the order of receiving the notifications when notifications of them are received, then a malfunction may occur in the corresponding component.
For example, when the residual amount of paper sheets in a paper cassette reaches zero, this status is notified; and when a user pulls out the paper cassette, fills up the paper cassette with paper sheets and closes the paper cassette, the status of the cassette closing is detected. Upon this, an end of the paper sheets in the cassette is lifted and it is detected, and it is notified of changing to lifting start status (notified that paper sheets are supplied). Since a status that the paper sheet residual amount is zero and the cassette is closed arises between the cassette closing and the lifting starting, a malfunction that another substitute paper cassette is selected occurs in the paper cassette selecting component.
Therefore, when an engine controller notifies the main controller of an event of the cassette closing, the main controller requests a current lifting status (a status dependent on an open/close status of the cassette) from the engine controller, and if the response indicates lifting is started, the main controller notifies the corresponding component of this status either earlier than or at the same time of the notification that the cassette is closed. Consequently, the aforementioned malfunction is prevented.
However, the main controller must perform such inquiry to the engine controller every time when the main controller receives a predetermined event. In the collective management, relatively many statuses, e.g. 180 statuses exist as notification objects and the notification is performed with the serial transmission to reduce the number of signal lines, and therefore, traffic congestion tends to occur in communication between the controllers and the inquiry results in further traffic congestion and a bottleneck.